We have all seen forensic scientists in TV shows, but how do they really work? What is the science behind their work?
The course aims to explain the scientific principles and techniques behind the work of forensic scientists and will be illustrated with numerous case studies from Singapore and around the world.
Some questions which we will attempt to address include:
How did forensics come about? What is the role of forensics in police work? Can these methods be used in non-criminal areas?
Blood. What is it? How can traces of blood be found and used in evidence?
Is DNA chemistry really so powerful?
What happens (biologically and chemically) if someone tries to poison me? What happens if I try to poison myself?
How can we tell how long someone has been dead? What if they have been dead for a really long time?
Can a little piece of a carpet fluff, or a single hair, convict someone?
Was Emperor Napoleon murdered by the perfidious British, or killed by his wallpaper?
*For Nanyang Technological University (NTU) students, please be noted that this course will no longer be eligible for credit transfer.

Taught By

Roderick Bates

Transcript

[MUSIC] This is our atomic absorption spectrometer. This compartment here houses the hollow cathode lamp which is the light source for the spectrometer. The central part of the instrument houses the flame. Currently, this is an acetylene oxygen flame, burning at about 1,000 degrees centigrade. [SOUND] And the sample dissolved in water or acid travels up this little tube here and then on upwards, into the flame. The light from the hollow cathode lamp passes through the flame, into this section of the instrument where we have the detector. It's not just the electrons of the atom that can be used for analysis. We can also use the nucleus of the atom, and this is the basis of a technique called Neutron Activation Analysis. In this technique we need to irradiate the sample with neutrons. The neutrons [SOUND] hit the nucleus of the atoms in the sample. And just as the electrons were put into excited states the nucleus is also excited. It becomes a compound nucleus. This compound nucleus then decays, giving out a gamma ray. And typically will become a radioactive nucleus, which can then give out a gamma ray later on. And it will ultimately end up as a product nucleus. Just as the radiation given out by the electrons was characteristic, so the gamma rays given out by these nuclei is also characteristic. So if we measure the energy of the gamma rays given out, we can once again analyze the element. So it's a good technique in that it is non-destructive of your sample. But it does have a serious disadvantage. In order to get the neutrons to do this analysis, you do need to have a nuclear reactor. If you don't have a nuclear reactor then you really can't do this method. So the output from neutron activation analysis looks like this. On the x axis, this is the energy of the gamma rays given out, and you can see that different elements give quite distinct peaks. So this particular sample here which is an archeological sample contains elements such as scandium, iron, cobalt, sodium and some minor elements as well.

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